Download Mgr Agnieszka Chruścikowska

Mgr Agnieszka Chruścikowska
Evaluation of human health threats
generated by food pests Plodia interpunctella
in the dwellings and the buildings of public use
Summary
Introduction
Food pests from the Pyralidae group, occur around the world, in different areas where the
stored food are located, eg.: in mills, bakeries, factories producing foodstuffs, in storage areas,
shops. Insects may occur in our homes - mainly in kitchens and pantries, and in public
buildings such as: in the social rooms of offices , schools , warehouses pharmacy, in hospital
kitchens, food storage areas , etc.
During the last several years, we observed the increased activity of the moth pests in
human household environment through the whole season. These insects are active during all
year. Various environmental factors influence on the life-cycle of Plodia interpunctealla,
which promotes higher temperature, but the larvae can survive at temperatures lower than
10°C, even outdoors. The development of first- generation of Plodia interpunctella in season
lasts approx. 2.5 - 3 months; second generation of Plodia interpunctella usually develops
longer than 6 months; Plodia interpunctella moths can produce more than two generations per
year in favourable conditions
The larvae of Plodia interpunctella can use different types of food: pastas, rice,
groats, breakfast cereals, oatmeal, spices, etc.. Also we can find the larvae in confectionery
products: biscuits, cookies, chocolate, candy. Plodia interpunctella moths dwell in a dry pet
food for dogs, cats , birds, fish , etc .
The presence of live larval and adult forms or/ and their body parts are considered
major contaminants in the food industry. Food losses in stored food supplies caused by these
insects are approx. 10% of world production.
The larvae spin massive amounts of silk that may accumulate impurities. These larvae
are causing severe damage to stored food : damaged grains and seeds of various plants are not
suitable for sowing. Products contaminated with feces and silk, change taste and smell.
Various chemicals used against pests from the Pyralidae group, but their effectiveness is
limited; It said emergence of resistance of insects against a number of insecticides.
Economic losses are a major aspect of research. There has not been a systematic studies on
Plodia interpunctella to determine if moths can transmit microorganisms potentially
pathogenic for human health.
The aim of study
Evaluation of human health threats generated by food pests Plodia interpunctella in the
dwellings and the buildings of public use.
For the implementation of the major aim detailed aims were determined:
- Examination in dwellings and building of publics, if in/on Plodia interpunctella forms may
occur microorganisms;
- Evaluation of individual objects in terms of prevalence of insects, which transmit the
microorganisms;
- Examination in individual dwellings and building of public use, if development forms of
Plodia interpunctella may transmit microorganism potentially pathogenic for human health
and assessment of prevalence infected insects in individual sites;
- Assesment of susceptibility and resistance of bacteria and molds isolated from the Plodia
interpunctella moths;
- Assesment of role examined insects in the transmission of allergenic species;
- Determining the specific recommendations connection with the threat hygienic generated by
Plodia interpunctella moths.
Material and Methods
Adult moths and larvae of Plodia interpunctella have been collected for the studies in
various urban and suburban dwellings in Poland, from January 2011 till March 2015.
The places where moths were captured have been assessed for building type, age of
building, size of the flat, the number of residents, presence of animals in the house, frequency
of clearing up, the air temperature.
The imago forms were taken directly during flight. Many adult forms from examinated sites
were also collected with application of pheromone traps. Larvae were captured directly from
food products.
Performed microbiological and parasitological examinations.
To detect bacterial and fungal strains, the conventional in vitro techniques were used. The
bacteriological agar and agar with 5% defibrinated sheep blood, Chapman’s plate growth
medium for recovery/ isolation of Staphylococci, and Mc’Conkey’s medium for identification
of Enterobacteriaceae were applied.
To detect fungi, Sabouraud medium and Chromagar -Candida BBL plates were used.
Species identification of microorganisms based on examination of the microscopic
preparations and in vitro cultures.
Due to the fact that the previous studies (standard microbiological techniques in vitro) showed
that the most frequently found are Aspergillus species, scheduled to run tests for their
identification at the molecular level.
Commercial kit for DNA isolation from tissue was applied (NucleoSpin, Macherey-Nagel,
Düren, Germany). PCR was carried out. The PCR products were observed under UV light in
2% agarose gel stained with ethidium bromide.
Standard antibiotic discs (Becton-Dicinson) were used to mark, with the disc diffusion methods, in vitro susceptibility and resistance of bacteria isolated of the Plodia
interpunctella moths to antimicrobial agents: penicillin G, aminoglycosides - streptomycin,
gentamicin; fluoroquinolone – ciprofloxacin, macrolide - erythromycin. Resistance and
susceptibility of fungi to several antifungal drugs: macrolide amphotericin B; azoles fluconazole, ketoconazole, itraconazole;
fluorinated piramidine -flucytozine, were also
tested; standard antifungal filter-paper discs (Biomed, Kraków) were applied.
Some adult moths and larvae were examined on the ultrastructural level to confirm the
presence of microorganisms on the body surface of insects at the ultrastructural level.
Samples were examined in LEO 1430VP scanning electron microscope (Zeiss).
To detect protein fractions giving positive reactions with IgE antibodies in sera, the SDS
PAGE and western blot methods were used.
Statistical analyzes were performed using the statistical program SPSS 21. The study used
multipartite tables and Pearson Chi2 test to compare some differences in terms of the presence
of microorganisms.
Results
In all, 1304 Plodia interpunctella adult moths and 154 larvae have been collected and
examined.
In the larvae and adult Plodia interpunctella forms were microorganisms which have been
identified as opportunistic bacteria and fungi potentially pathogenic for humans. In Plodia
interpunctella, strains Gram-positive bacteria Enterococcus faecalis, Micrococcus luteus,
Bacillus cereus, strains of Gram-negative bacteria: Klebsiella oxytoca, Escherichia coli, and
the fungi Aspergillus, Penicillium, and yeast Candida albican, were detected. Especially often
were detected the molds of Aspergillus, mainly allergenic strains of Aspergillus niger.
Aspergillus species on / in adult Plodia interpunctella, caught in the dwellings, occurred more
frequently than on/in adult Plodia interpunctella from public buildings (32% vs 23%).
In molecular studies the products size varied and showed about 600 and 610 bp. This
fragment size suits the size of the products characteristic for a few Aspergillus species: A.
flavus, A. fumigatus and A. niger.
Scanning electron microscope examination revealed the presence of numerous
fungal filaments and pellets on surface of Plodia interpunctella imago and larvae.
Strains of bacteria and fungi found in developing forms of P. interpunctella.
They differ in sensitivity / resistance to antibiotics, antimicrobial agents and other
chemotherapeutic agents; some of them showed a marked drug resistance.
In the examined sera, the positive reactions of IgE antibodies for 15 protein fractions
of Plodia interpunctella have been shown.
The strongest reaction for protein fractions 45.197 – 44.718 kDa has been shown.
Summary and conclusions
The above mentioned results of the study indicate that contamination of stored food products
by developmental forms of Plodia interpunctella may cause not only economic losses in
foodstuffs. Plodia interpunctella moths are reservoirs opportunistic bacteria and fungi that are
factors of serious health risks, especially for people with weakened immune system.
Among potentially pathogenic bacteria in Plodia interpunctella it should be pointed
detection of Enterococcus faecalis, Escherichia coli and Klebsiella oxytoca.
E. faecalis bacteria can cause abscesses, severe infections of the urinary tract, biliary and
endocarditis, particularly in people with weakened immune systems. Escherichia coli bacteria
may cause piratory tract infections, urinary tract infections, severe diarrhea in adults and
children, also cause sepsis. Klebsiella oxytoca in conditions of immunodeficiency can cause
severe infections, including: sepsis, endotoxin shock, pneumonia, pulmonary abscesses,
infections of the urinary tract, biliary tract, inflammation of the sinuses, middle ear.
Also in adult forms and lavae of Plodia interpunctella, Aspergillus, Penicilium Candida
strains were detected.
The Aspergillus molds are recorded as the causative agents of asthma and serious pulmonary
infections; liver failure, causing jaundice and breathing difficulties may also occur.
Molds of Penicilium sp. producing spores are believed to be causative agents of non–food
allergies which intensity of symptoms is connected with changes in spore production and
severity of the disease depends on the immunological status of the infected individual.
The Candida molds can cause infections with a very broad spectrum, from harmless skinmucosal surface to multiple organ that threaten the patient's life.
It should be pointed out that the phenomenon of resistance of bacteria and fungi found in
Plodia interpunctella, is dangerous particularly for people with impaired immune system.
In the fight against these pests is very important to comply with the conditions of hygiene laid
down by law, has become the food inspection, sanitary measures, e.g. frequent cleaning and
appropriate choice of packaging.
Conclusions
1. P. interpunctella developmental stages were detected in all examined dwellings and
buildings of public use. We observed abundance of P. interpunctella populations in
the various locations. The greater the intensity of the infestation has been found in
homes, less pest was detected in public buildings. The larvae and their silk have been
found in various food products, usually in the groats and rice.
2. Both in / on adults and larval forms of pests occurred micro-organisms which have
been identified as opportunistic bacteria and yeasts and molds potentially pathogenic
for humans.
3. In vitro microbiological techniques, molecular (PCR) and scanning electron
microscope (SEM) showed the presence in / on the test insects mainly opportunistic
allergenic Aspergillus strains A. niger. A. flavus, A. fumigatus.
4. Adult Plodia interpunctella caught in households contain more molds of
the
Aspergillus than from buildings of public use. A temperature of 20°C - 25°C may be a
factor to development of Plodia interpunctella and also higher prevalence of the pests.
5. Opportunistic fungi of the Candida and Aspergillus genera are the factors of serious
human diseases, particularly dangerous for people with weakened immunosystem.
Strains found in P. interpunctella showed some resistance to antimicrobial agents.
6. In buildings of public use, in particular related to health services, in addition to the
aforementioned recommendations, pest foods as potential vectors of nosocomial
infections should be treated as a permanent and indispensable element of hospital
hygiene.
7. Due to the seriousness of the problem should be conducted further research
undertaken direction. This will allow to expansion of current knowledge and provide
new knowledge about human health threats generated by Plodia interpunctella. These
studies would have practical significance for the prevention / limitation of dispersion
of dangerous for human health pathogens and allergenic species .